We took 2 booster seats in a big duffle bag as checked baggage. Even threw some clothes and stuff in around them. Even if you have to pay for checked baggage, it is MUCH cheaper than renting from a car rental company!!

We put our two boosters in a highback booster cover and fit in extra shoes and pool toys around the empty spaces. We checked ours. It was very easy. I also saw people checking them and the airline put them in big plastic clear bags to keep them from getting dirty.

Most airlines, including AirTran (gasp) will not charge a bag fee if you're checking a car seat. With two little ones and one adult I would recommend checking the seat you won't be using on the plane. I bought a large car seat bag with a handle for that reason.

FYI that if you are a AAA member, using the AAA CDP with Hertz includes one child seat (infant, toddler, booster) in the rate. I've done this several times now, and sure, the seat isn't going to be as good as your personal seat, but boy, it sure beats lugging one around.

When we went last year we had 2 in boosters with no back and one in a booster with a back. We were able to pack the 2 boosters with no back in one suitcase with clothes, diapers...etc. and check it as a bag. With the high back booster we took the back off and put it in a seperate suitcase with more clothes and checked it as well. Since we had 5 paying people on Southwest we were allowed 10 bags for free and we didn't need that many so we ended up with 2 being just clothes and 2 being seats and clothes. We didn't want to gate check because we didn't want to have to lug them through the airport...and with them being in suitcases and surrounded by clothes they were pretty well protected from any abuse they luggage might have received.

On a side note...our flight out of MCO was delayed due to a major storm and one of the carts that still had luggage on it was out on the runway (we were watching from the terminal window)...and with the high winds there were several carseats and booster seats not in suitcases getting drenched because they were thrown off the luggage cart during the storm. Not sure why they couldnt have taken the luggage cart back inside instead of just abandoning it like they did but I was definetly glad ours were in suitcases because of that.